/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatform.h
A 16-bit character type. In-memory only. 16-bit representation. Should really be char16_t but making this the generic option is easier for compilers which don't fully support C++11 yet (i.e. MSVC).
typedef [uint16](API\Runtime\Core\GenericPlatform\FGenericPlatformTypes\uint16) CHAR16